Q. I have a tropical hibiscus plant that has developed white sticky spots on the leaves and stem. We had the plant outside during the summer, and then brought it indoors last fall. What’s going on? A.Q. It seems as if every year my tomato plants develop dark spots on the lower leaves. The leaves turn yellow, then brown, and then fall off. Gradually the problems progresses upwards until the whole plant is toast. What is going on?
A. Tomato plants are susceptible to a wide variety of fungal leaf spots and blotches. With all the rainfall we have experienced this year, even if you did everything else correctly, one can still have infected plants. Currently, we are receiving many diseased tomato samples at the Extension office.
Two very common diseases of tomato are Early Blight and Alternaria leaf spot. Both develop on the lower leaves from fungal spores blown around and splashed up from the soil. If nothing is done, more leaves are infected and pretty soon the whole plant becomes bare and stunted. Fruit development is poor.
The plant will just waste away.
Some folks ask, “Where did the fungal spores come from?” Fungal pathogens are everywhere. When weather forecasters talk about mold counts, some of the mold is made up of the spores of fungi that can infect specific plants.
Prevention of fungal diseases of tomato is the key to success. Use a mulch of clean straw or pine needles under the tomato plant. This practice can help prevent splashing of fungal spores up on the plant. Water the plants during the day – never in late afternoon or evening. Watering late in the day or at night can promote disease because fungal spores love water.
When the tomato begins to set fruit, scatter one cup of Epsom salts on the soil near the plants and water it in. Epsom salts may provide some additional minerals that tomatoes prefer at a stage when the plant really wants them.
Use a fertilizer made for tomatoes and avoid over-fertilization of the plants. Sometimes if too much high nitrogen fertilizer is used too often, then the lush growth produced by over-fertilization can be more susceptible to disease.
One can also pick off diseased leaves when they appear. Sometimes this stops the process. Use a fungicide registered for use on tomatoes if all else has failed. Make sure to read and follow label directions before using.
Most fungicides only prevent disease, so don’t expect the spray to “cure” the problem.
The sprays – along with the other methods I have mentioned – can help to ensure that the plant is healthy.
